Poor biobehavioral self-regulation likely contributes to a number of unhealthy behaviors as individuals seek and consume substances that improve self-regulation at a neurobiological level. Poor self-regulation begins very early in the lifespan, at a time when food is the only accessible substance with biological properties that aid the individual's ability to self-regulate. Children with poor self-regulation may therefore be more likely to tantrum for food, overeat and become overweight. There have been no studies to date integrating knowledge of biobehavioral self-regulation with eating behavior, dietary intake and weight status in early childhood. The study team was awarded a Challenge Grant in 2009 to examine some of these associations in low-income 3- to 5-year-olds, and the preliminary results of this project already demonstrate robust associations between aberrant diurnal salivary cortisol patterns, food-related tantrums, and overweight, beginning at age 36 months. In this low-income population, 40 percent of the children are already overweight by age 36 months, and a significant increase in overweight prevalence seems to occur around age 24 months. This application, therefore, proposes to collect measures of salivary cortisol and alpha amylase, self-regulation, eating behavior, diet, and anthropometry from 250 low-income children longitudinally at ages 21, 27, and 33 months. The study will provide more in-depth measures of these constructs from a younger cohort than has ever previously been studied, and in the low-income demographic that is at very high risk for both poor biobehavioral self-regulation and obesity. Structural equation modeling will be used to examine these potential associations. The aims are to examine, among low-income toddlers longitudinally: (1) the relative contributions of food-related self-regulation, non-food related self-regulation, and salivary cortisol and alpha amylase to preference for comfort foods, emotional eating behavior, and weight status, and to determine if these relationships differ across ages 21, 27, and 33 months; (2) relationships between biobehavioral markers of self-regulation at 21 months with changes in weight status between 21 and 33 months, mediated by preference for comfort foods and emotional eating; (3) trajectories of the development of behavioral self-regulation, and to determine if these trajectories are associated with differences in preference for comfort foods, emotional eating behavior, and weight status at 33 months, independent of physiological markers of self-regulation at baseline. The results of this study will have implications for understanding biobehavioral mechanisms of excessive weight gain in toddlerhood, and thereby potentially contribute to more effective, novel, targeted prevention approaches. The results will also improve the understanding of contributors to health disparities based on socioeconomic status and may also have broad implications for the prevention of a wide range of unhealthy behaviors associated with difficulties with biobehavioral self-regulation.